Proteremaeus mongolicus (Golosova)

Badamdorj, 2003, The soil mite family Eremaeidae (Acari: Oribatida) in Mongolia, with remarks on distribution and diversity of known genera, Journal of Natural History 37, pp. 1571-1610 : 1595-1600

Proteremaeus mongolicus (Golosova)

(figures 14–16)

Sibiremaeus mongolicus Golosova, 1983: 1903 , figure d.

Proteremaeus mongolicus: Behan-Pelletier and Ryabinin, 1991: 561 .

Diagnosis. Medium-sized (520–592 m m) species with typical characters of Proteremaeus . Costulae long, relatively thick, widely spaced, nearly parallel; sensilli medium long, slightly expanded distally in distinctly barbed, narrowly clavate head; lamellar and interlamellar setae medium long, barbed; exobothridial setae short, thin, smooth; notogaster narrowing posteriorly; 10 pairs of thin, finely barbed notogastral setae; postanal process V-shaped; posteromarginal sclerite not evident; genua I–III and tibiae II and IV with setae d coupled with respective solenidia.

Measurements. Body length 520–592 (547) m m; length of notogaster 344–368 (360) m m; width of notogaster 248–269 (256) m m. Eleven specimens were measured.

Integument. Body colour reddish to deep reddish brown. Dorsal and ventral plates and leg segments with relatively thin granular cerotegument. Microtuberculate in interlamellar region, lateral part of lamellar costulae and around leg acetabula. Notogaster and ventral plate weakly foveate.

Prodorsum. Rostrum smoothly rounded in dorsal view, but slightly projecting anteroventrally in lateral view. Rostral seta thin, 44–50 m m long, barbed. Lamellar seta barbed, shorter and thinner than ro (30–34 m m). Costula 74–76 m m long, relatively thick, widely spaced, nearly parallel. Distance between costulae almost equal to or very slightly less than costular length. Interlamellar seta 38–40 m m long, barbed. Distance between bases of in–in less than that of le–le. Exobothridial seta about 19–21 m m long, thin, smooth. Sensillus 60–80 m m in length, slightly expanded distally in distinctly barbed and narrowly clavate head (figures 14A, 16A).

Notogaster. Elongate oval, about 1.3–1.4 times as long as wide. Anterior margin nearly straight or slightly rounded, outline narrowed posteriorly. Humeral projection well developed. Ten pairs of medium long (34–42 m m), thin, finely barbed notogastral setae with small porose rings basally; setae of ps series nearly equal to or slightly shorter than other setae. Opisthosomal gland opening and lyrifissures ia, im, ih, ip and ips well developed. Posteromarginal sclerite not evident (figures 14A, B, 16B).

Gnathosoma . Infracapitular mentum almost as long as wide, without noticeable microtubercles. Hypostomal setae a, h and m thin, smooth (figure 14B). Chelicera and palp normal for genus, similar to those of P. jonasi Piffl ; palpal setation: 0-2-1-3-9(1).

Epimeral region. With many muscle sigillae. Sejugal, II and III apodemes well developed, aligned obliquely. Epimeral setal formula 3-1-3-3, all setae long, smooth. Discidium well developed, subtriangular, slightly pointed distally. Pedotectum I slightly projecting, pedotectum II bifurcate distally in dorso-ventral view (figure 14B).

Ano-genital region. Genital aperture nearly oval, about 1.2× as long as wide; anal aperture widened posteriorly, about 1.4× as long as wide. Ano-genital setae relatively short, smooth; anal and adanal setae with small porose rings basally. Postanal process relatively narrow, V-shaped (figures 14B, 16B).

Legs. Measurements of leg segments given in table 4. Setae d present on genua I–III and tibiae II and IV, coupled with respective solenidia; seta d absent from tibia III. Femora I–IV and trochanters III and IV with large porose areas. Tarsi and tibiae I–IV with relatively small porose areas. Formula of leg setation (including famulus) I (1-5-3-4-19), II (1-5-4-4-17), III (2-3-2-3-15); IV (1-2-2-3-12); formula of solenidia: I (1-2-2); II (1-1-2); III (1-1-0); IV (0-1-0). Structure and setation of legs I–IV as shown in figures 14D, 15A–C, 16C, D.

Material examined. Eight specimens: Mt Khustai, District Altanbulag , Central Province , litter of birch forest ( Betula platyphylla Sukatchev, 1911 ), 47°42∞N, 106°25∞E, elevation 1680 m, 25 May 1998; two specimens : Mt Orog Yamaat, Nature Reserve ‘ Gorhi Terelj’ , District Erdene , Central Province , decaying wood in birch forest ( Betula platyphylla Sukatchev, 1911 ), 48°10∞N, 107°30∞E, elevation 1750 m, 21 July 1998; three specimens : Mt Bogd Khan, Central Province , 6 km south of Ulaanbaatar, litter of larch forest ( Larix sibiricus Ledebour, 1833 ), 47°55∞N, 106°30∞E, elevation 1650 m, 26 March 1997 , Leg. B. Bayartogtokh .

Remarks. The original descriptions of two species, P. mongolicus and P. chadaevae by Golosova (1983) are insufficient for recognition and, therefore, it is difficult to diagnose them. Golosova (1983) illustrated only a dorsal view for each species and, according to the description and figures, the notogaster of P. mongolicus is longer and narrower than that of P. chadaevae . Also, some other differences can be found between these two species: e.g. lamellar and notogastral setae of P. mongolicus are distinctly barbed as opposed to the smooth setae in P. chadaevae ; notogaster distinctly narrowed posteriorly as opposed to the widened and inwardly curved posterior margin in P. chadaevae ; presence of distinct transverse ridge-like structures anterior and posterior to the insertions of setae le as opposed to absence of such structures in P. chadaevae .

According to the features treated by Golosova (1983), the present material seems conspecific with P. mongolicus , because most characters are similar in the specimens studied here. However, some characters of the present material are not congruent with Golosova’s description. In the descriptions of both P. mongolicus and P. chadaevae, Golosova (1983) showed distinct ridges outside the costulae, i.e. along lateral and anterior margins of the prodorsum, but the text did not mention these. These ridges are probably artifacts of the observation, due to a change in contour, e.g. a swelling on the prodorsum. Reinvestigation is necessary. Also, she illustrated two transverse ridges on the prodorsum of P. mongolicus , one situated anterior to the costulae and the other posterior to the insertions of the lamellar setae. The posterior ridge looks more strongly developed than the anterior, and was illustrated by two parallel solid lines. I am not convinced this is a real structure, because no other known species of Proteremaeus show a transverse ridge posterior to the insertions of the lamellar setae. Further study of this structure is also needed.

As mentioned above, the type localities of this and the other species described by Golosova (1983) are uncertain. In the description of P. mongolicus , she mentioned that (in Russian) ‘One female (holotype), in larch forest, mouth ‘El’, 6. VII. 1971 (Z. V. Chadaeva)’. On the basis of these brief data, I supposed that the type locality of this species is Mouth ‘Yol’ in Mt Gurvan Saikhan, District Bayandalai, South Gobi Province. This is a dry desert area in the southern part of Mongolia, but there is no larch forest. I have a small number of collections from this locality, but they contain no species of Proteremaeus .

Concerning the other species P. chadaevae, Golosova wrote (in Russian) ‘ one male (holotype), in the soil under grasses (East Khangai) 6.VII.1971 (Z. V. Chadaeva)’. These data are inexact because ‘ Khangai’ is a very large mountainous area in the central part of Mongolia, and there is no standard division, like East Khangai. In spite of these unclear data, I suspect that Z. V. Chadaeva (a participant of the Russian and Mongolian Joint Biological Expedition , initiated in 1970) might have collected her samples from a field research site situated in the territory of District Tuvshruuleh , Province Arkhangai ( East Khangai is the unofficial name for this area used by Russian researchers). I have not yet collected samples from this area. Thus , no material of this species was available for the present study. Moreover , the date of collections given in Golosova’s work seems to be incorrect, because the Khangai and South Gobi areas are situated very far from each other (at least 400 km), and there is little possibility that collections from these two localities were taken within the same day .

Distribution. Known from cool temperate forests and grassland habitats in Central Mongolia.